The present invention relates to silicon tubular bodies and more particularly to methods of partially or totally closing the ends of such devices.
The manufacture of silicon tubes is described, for example, in Keller et al. U.S. Pat. No. 3,781,152. Such devices are commonly made by depositing silicon from as phase reduction of chlorosilanes with hydrogen on a heated mandrel such as graphite and have found application as furnace tubes for semiconductor device manufacturing, for example. For some applications it is desirable that such tubes be provided with closed ends. There is also sometimes a need for attachment to other devices such as feed lines, for example, and this is difficult with open end tubes.
U.S. Pat. No. 3,751,539 to Reuschel et al. discloses a method of making a closed end silicon tube by vapor deposition, then welding a silicon wafer across the tube end and then depositing additional silicon. This method, however, requires two separate deposition steps plus removal from the reactor between the two steps to effect the welding. This obviously requires substantial labor as well as energy loss in the multiple handing and heating. Additionally, it has been found that the uneven heating inherent in R.F. welding causes thermal stresses which often result in cracking.
The Czochralski method for growing crystals from a melt by dipping a seed in the melt is well known and used extensively in producing silicon crystals for the semiconductor industry. Examples of the Czochralski process are shown in Sparks et al. U.S. Pat. No. 2,631,356 and Rosi U.S. Pat. No. 2,889,240.